When choosing an aluminum alloy for a project, it’s important to consider the attributes you need for the final application – whether it’s strength, corrosion resistance, conductivity, or a combination of these qualities. 7075 aluminum and 6061 aluminum are two common types of alloy in the industry that are worth comparing.
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What is the Chemical Composition of Both Aluminum Alloys?
7075 aluminum alloy is part of the 7xxx series, where zinc and copper are used as the primary alloying elements. 6061 aluminum is part of the 6xxx class of aluminum, which use magnesium and silicon as their primary alloying elements. Here is a full breakdown of 7075 aluminum vs 6061’s chemical composition:
| ||7075 Aluminum||6061 Aluminum|
|% Aluminum (Al)||90.0% Al||97.9% Al|
|% Zinc (Zn)||5.6% Zn||—|
|% Magnesium (Mg)||2.5% Mg||1.0% Mg|
|% Chromium (Cr)||0.23% Cr||0.2% Cr|
|% Copper (Cu)||1.6% Cu||0.28% Cu|
|% Silicon (Si)||—||0.6% Si|
Comparing the Characteristics of 7075 Aluminum vs 6061 Aluminum
Impressive strength is 7075 aluminum’s notable trait. This alloy is one of the strongest types of aluminum available, and it is difficult to form and weld. 7075 has average-to-good ratings for machinability, corrosion resistance, and anodizing response. 6061 aluminum is one of the most popular aluminum grades available because of its good strength, formability, weldability, machinability, and corrosion resistance. Here is a rundown comparing their characteristics.
How Strong Are They?
When looking at both alloys in the “T6 condition” (meaning that the material is heat-treated with a solution, then it is aged), it’s noticeable that 7075 T6 aluminum properties feature a tensile strength that is nearly double that of 6061 T6 aluminum properties. The shear strength of 7075-T6 is estimated to be 1.5 times that of 6061-T6. 7075 T6 aluminum is substantially harder as well.
Can You Machine Them?
The machinability of a material is a measure of how it reacts to machining procedures such as milling, cutting, die-casting, and more. Both of these alloys can be machined without much trouble, but 6061 aluminum is the preferred choice if machinability is desired. 6061 aluminum is believed to have good machinability, while 7075 aluminum would be rated as fair.
Can They Be Formed and Welded?
With the presence of magnesium with silicon as its principal alloying elements, 6061 aluminum has good formability and weldability. 7075 aluminum, as a much harder material with a higher zinc content, is not as conducive to forming and welding. However, in the annealed condition, this grade can be formed and heat-treated if necessary, as well as welded in place.
How Corrosion Resistant Are They?
When exposed to air or water, 6061 aluminum alloy forms a layer of oxide which renders it nonreactive with elements that are corrosive to the underlying metal. However, due to the copper content of 6061, it is slightly less resistant to corrosion than other alloy types. Some corrosive effects can be removed entirely by coating the 6061 aluminum alloy with a protective layer.
Can They Be Anodized?
Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. 6XXX Series alloys like 6061 aluminum are excellent candidates for anodizing. The oxide layer that follows the anodizing process is transparent and offers excellent protection. 7075 Aluminum also takes to the anodizing process very well. The subsequent oxide layer is clear and offers great protection. If the zinc level becomes excessive, however, the oxide layer created by anodization can turn brown.
|Forming & Fabricating–Corrosion Resistance|
|Alloy||Sheet Only (Forming||Machining||Resistance||Arc w/ Inert Gas||Brazing||Soldering||Rural||Industrial||Marine||Sea Water|
Understanding the Ratings
Ratings A through E are ratings that are relative in decreasing order of merit. They are based on exposures to sodium chloride solution by immersion or intermittent spraying. You can use alloys in industrial and seacoast atmospheres without protection if they have ratings of A or B. You should protect alloys, at least on surfaces with joints, if they have C, D, or E ratings. This data was pulled from the 2013 Aluminum Standards & Data. For more information, please refer to documentation by the Aluminum Association.
Applications of 7075 Aluminum vs 6061 Aluminum
While it may not offer the same formability and weldability as other aluminum alloys, 7075 aluminum excels in high-stress applications where strength is important. 7075 aluminum is often called “aircraft grade” because it’s one of the highest-strength aluminum alloys available. It is typically used in aircraft, missiles, spacecraft, and other defense applications. It also shows up in other parts subject to high wear, structural materials, and military applications.
Because of its versatility, workability, strength, corrosion resistance, and joinability, 6061 aluminum shows up in a wide range of all-purpose applications, including structural materials, welded assemblies, piping, fasteners, electronic parts, and more. It is frequently used across a range of industries and applications.
You’ll typically find 6061 aluminum in:
- shipbuilding – sailboats, yachts, marine fittings, and hardware
- automotive – truck and bus bodies, wheels, brakes, and hydraulic pistons
- aircraft structures and fittings
- railway car components
- appliance fittings
- food and beverage cans
6061 aluminum is available in aluminum bar, aluminum tube, and aluminum plate. We invite you to learn more about 6061 aluminum bar and 6061 aluminum plate.
Density of 6061 aluminum vs 7075
Density is one characteristic to consider when comparing the physical properties of 7075 aluminum and 6061 aluminum.
The density of 7075 aluminum is slightly larger than pure aluminum at 2.81 g/cm3 (0.102 lb/in3), and it can also be strengthened using the heat treatment process (the most common temper being 7075-T6).
The density of 6061 aluminum alloy is 2.7 g/cm3 (0.0975 lb/in3), or about the same as pure aluminum metal.
Mechanical Properties of 6061 Aluminum vs 7075 Aluminum
|Type 6061 Aluminum Alloy||Type 7075 Aluminum Alloy|
|Yield strength||276 MPa||40,000 psi||503 MPa||73,000 psi|
|Modulus of Elasticity||68.9 GPa||10,000 ksi||71.7 GPa||10,400 ksi|
|Thermal conductivity||167 W/m-K||1160 BTU-in/hr- ft²-°F||130 W/m-K||900 BTU-in/hr-ft²-°F|
|Melting point||582 – 652°C||1080 – 1205°F||477 – 635°C||890 – 1175°F|
|Electrical resistivity||3.99 x 10-6 ohm-cm||5.15 x10-6 ohm-cm|
Thermal Conductivity of 7075 Aluminum vs 6061
Thermal conductivity is a measure of how well heat is transferred through a material (how well it conducts heat). Both 6061 aluminum and 7075 aluminum are heat treatable. It is interesting to note that even though 7075 aluminum is much stronger than 6061 aluminum, it melts at a slightly lower temperature.
Because 6061 aluminum has a higher thermal conductivity than 7075 aluminum, it can be a better choice for certain applications. Of the heat-treatable alloys, 6061 aluminum plate is one of the more versatile and is commonly used for its corrosion resistance and high toughness.
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